DNA ligase III is recruited to DNA strand breaks by a zinc finger motif homologous to that of poly(ADP-ribose) polymerase -: Identification of two functionally distinct DNA binding regions within DNA ligase III
DNA ligase III is recruited to DNA strand breaks by a zinc finger motif homologous to that of poly(ADP-ribose) polymerase -: Identification of two functionally distinct DNA binding regions within DNA ligase III
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DOI：
10.1074/jbc.274.31.21679
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发表时间：
1999-07-30
影响因子：
4.8
通讯作者：
Tomkinson, AE
中科院分区：
文献类型：
--
作者：
Mackey, ZB;Niedergang, C;Tomkinson, AE
哺乳动物 DNA 连接酶由两侧不相关序列的保守催化结构域组成。在催化结构域的C末端，有一个16个氨基酸的序列，称为保守肽，其在连接反应中的作用尚不清楚。在这里，我们表明该基序 C 末端的保守带正电残基是酶-AMP 形成所必需的。这些残基可能与 ATP 的三磷酸尾相互作用，使其适合活性位点赖氨酸的亲核攻击。 RFPR 序列中的氨基酸残基在哺乳动物 DNA 连接酶的保守肽中是不变的，在随后产生 DNA-腺苷酸中间体的核苷酸转移反应中发挥着关键作用。 DNA 连接酶 III 的 N 末端锌指与聚 (ADP-核糖) 聚合酶的两个锌指同源，因此 DNA 连接酶 III 的 N 端锌指与 DNA 的结合对于 DNA 连接酶的体外或体内活性不是必需的。然而，这种锌指使 DNA 连接酶 III 能够在生理盐浓度下与带切口的 DNA 相互作用并连接。我们认为，在体内，DNA 连接酶 III 锌指可能会取代 DNA 链断裂处的聚（ADP-核糖）聚合酶，从而实现修复。
Mammalian DNA ligases are composed of a conserved catalytic domain flanked by unrelated sequences. At the C-terminal end of the catalytic domain, there is a 16-amino acid sequence, known as the conserved peptide, whose role in the ligation reaction is unknown. Here we show that conserved positively charged residues at the C-terminal end of this motif are required for enzyme-AMP formation. These residues probably interact with the triphosphate tail of ATP, positioning it for nucleophilic attack by the active site lysine. Amino acid residues within the sequence RFPR, which is invariant in the conserved peptide of mammalian DNA ligases, play critical roles in the subsequent nucleotidyl transfer reaction that produces the DNA-adenylate intermediate. DNA binding by the N-terminal zinc finger of DNA ligase III, which is homologous with the two zinc fingers of poly(ADP-ribose) polymerase, is not required for DNA ligase activity in vitro or in vivo. However, this zinc finger enables DNA ligase III to interact with and ligate nicked DNA at physiological salt concentrations. We suggest that in vivo the DNA ligase III zinc finger may displace poly(ADP-ribose) polymerase from DNA strand breaks, allowing repair to occur.